JPWO2018212093A1 - Engine unit - Google Patents

Abstract

An intake pipe fuel injection type four-stroke engine unit capable of improving the startability of the engine 10 in which a high load area TH and a low load area TL exist between four strokes. A four-stroke engine body 10 having a high load area TH and a low load area TL between four strokes, a permanent magnet starter motor 30 having a permanent magnet and rotating a crankshaft 46, and a permanent magnet starter motor 30 4 measured by the engine temperature sensor 28 during the low load region TL and after the fuel injection device 54 injects fuel into the intake passage 33a and until the intake valve 50 closes. The rotational speed of the permanent magnet starter motor 30 is controlled to suppress an increase in the rotational speed of the crankshaft 46 based on the temperature of the stroke engine body 10.

Description

  The present invention relates to an engine unit having a high load area and a low load area for four strokes and starting by cranking a crankshaft by a starter motor.

  A four-stroke engine (for example, a single-stroke engine) that has a high load area where the load for rotating the engine crankshaft is large and a low load area where the load for rotating the engine crankshaft is small for four strokes. Cylinder engines are known.

  Patent Document 1 (Japanese Patent Application Laid-Open No. 2003-343404) discloses an engine starting device for starting an engine by rotating a crankshaft in a forward direction after the crankshaft is once reversely rotated and stopped.

  In the engine starting device described in Patent Document 1, after the rotation of the crankshaft of the engine is stopped, the crankshaft reversely rotates to a position where the load increases in the reverse rotation, that is, to the middle of the expansion stroke. Thereafter, the engine starting device rotates the crankshaft forward by rotating the motor in the normal rotation direction from a position midway in the expansion stroke.

  As described above, by reversely rotating the crankshaft to the position where the load increases, ie, the position in the middle of the expansion stroke, the crankshaft from the middle of the expansion stroke to the compression stroke when the engine is started, It rotates in the low load area. Thereafter, the engine reaches the first high load area. Therefore, the rotational speed of the crankshaft can be increased before the engine reaches the first high load area. By utilizing both high inertia with high rotational speed and the output torque of the starter motor, the engine can overcome the first high load region.

  Further, according to Patent Document 2 (International Publication No. WO 2015/093576), after the combustion operation of the four-stroke engine main body is stopped, the crankshaft is rotated by a three-phase brushless motor when the crankshaft rotates forward. An engine unit is disclosed that provides resistance to normal rotation.

  The engine unit stops the crankshaft at a position of a compression stroke in the four-stroke engine body. Then, in response to the input of the start instruction at the time of stopping the crankshaft, the three-phase brushless motor rotates the crankshaft forward from the position of the stopping compression stroke.

  Thereby, when starting the four-stroke engine body in response to the input of the start instruction, the crankshaft is started to rotate from a position where the four-stroke engine can be easily started even if the output torque of the motor is small. Can.

  As described above, when the crankshaft starts to rotate in response to the input of the start instruction, the rotational speed of the crankshaft gradually increases from the stop state. When the positive rotation of the crankshaft is started from the compression stroke, in the compression stroke, the rotational speed of the crankshaft is low. As described above, when the rotational speed of the crankshaft is a compression stroke at a low speed, the crankshaft is unlikely to receive a compression reaction force by the gas in the combustion chamber. As a result, the crankshaft can rapidly rotate over the load in the high load area of the compression stroke.

Japanese Patent Application Publication No. 2003-343404 International Publication No. WO2015 / 093576

  The inventors evaluated the startability of the engine in which a high load area and a low load area exist between four strokes as shown in the above-mentioned Patent Documents 1 and 2. As a result, the present inventors have found that the startability of the engine is reduced due to the large load fluctuation in a specific situation.

  An object of the present invention is to provide a configuration capable of improving startability in the engine in which a high load area and a low load area exist during a 4-stroke cycle.

  The present inventors have evaluated the startability of an engine in which a high load area and a low load area exist during a 4-stroke, which has been proposed conventionally.

  In the engine, which has been proposed conventionally, in which a high load area and a low load area exist between four strokes, the inertia force obtained by accelerating the rotational speed of the crankshaft in the low load area is utilized. The startability of the engine is enhanced. Therefore, basically, the startability of the engine is good.

  However, the inventors of the present invention consider that in certain aspects, the load fluctuation of the engine is large, so by accelerating the rotational speed of the crankshaft in a low load area, conversely, the engine It has been found that the startability of

  Specifically, in the engine in which the high load area and the low load area exist during the four strokes, the rotational speed of the crankshaft accelerates in the low load area even if the engine temperature is extremely low. In particular, when the temperature of the engine is at a very low temperature, the load on the engine is further increased. Therefore, it is considered preferable to increase the inertia speed by increasing the rotational speed of the crankshaft in a low load region.

  However, if the rotational speed of the crankshaft is increased in a low load region when the engine temperature is at a very low temperature, the vapor pressure of the fuel is reduced due to the temperature decrease to suppress the vaporization of the injected fuel and the rotation of the crankshaft. The increased speed reduces the time from the start of fuel injection to the completion of the intake stroke. As a result, the amount of fuel flowing into the combustion chamber is reduced.

  As a result, the total heat generation amount of the fuel contributing to the combustion is reduced, so that the torque due to the combustion may not be obtained sufficiently, and the engine may not be able to start. Moreover, in the engine in which the high load area and the low load area exist between the four strokes, the same phenomenon may occur at the next combustion because the combustion interval is large.

  As described above, in the engine in which the high load area and the low load area exist during the four strokes, when the rotational speed of the crankshaft is accelerated in the low load area when the engine temperature is extremely low, the startability deteriorates. There is a case. The present inventors have found the above phenomenon in evaluating the startability of the engine where there is a high load area and a low load area during the stroke.

  As disclosed in Patent Documents 1 and 2, in the engine having a high load area and a low load area between four strokes, inertia obtained by accelerating the rotational speed of the crankshaft in the low load area. The power is used to enhance startability. When the engine temperature is at a very low temperature, the load on the engine is further increased, so it is unlikely to reduce the inertia force by suppressing the acceleration of the rotational speed of the crankshaft in the low load region.

  However, in the case of a permanent magnet starter motor, the lower the rotational speed, the higher the torque. The present inventors utilize the characteristics of such a permanent magnet starter motor to produce the crank when the engine temperature is extremely low in the engine in which a high load area and a low load area exist between four strokes. It has been found that the energy from the first combustion can be sufficiently increased even if the acceleration of the rotational speed of the crankshaft is suppressed in the low load region until the first combustion after the shaft rotates from the stationary state. Moreover, in the engine temperature region where the startability does not decrease, acceleration of the rotational speed of the crankshaft can be promoted in the low load region between the stationary state and the first combustion after the crankshaft is rotated. The same startability can be secured.

  Based on the examination result as described above, the present inventors considered the following configuration.

The present invention adopts the following configuration in order to solve the problems described above.
(1) An engine unit according to an embodiment of the present invention
A combustion chamber provided with an intake port and an exhaust port, an intake valve for opening and closing the intake port, an exhaust valve for opening and closing the exhaust port, air connected to the intake port and air in the atmosphere via the intake port , An exhaust passage connected to the exhaust port, a fuel injection device for injecting fuel into the intake passage, and ignition for igniting a mixture including fuel and air in the combustion chamber Apparatus, a piston reciprocating in the combustion chamber, and a crankshaft connected to the piston so as to rotate according to the reciprocating movement of the piston, a load rotating the crankshaft during four strokes 4 stroke engine having a high load area where the load is large and a low load area where the load that rotates the crankshaft is smaller than the load of the high load area. And down the body,
A permanent magnet starter motor having a permanent magnet and rotating the crankshaft;
A controller for controlling the permanent magnet starter motor, the fuel injection device, and the ignition device;
An engine temperature detection unit that detects the temperature of the four-stroke engine body;
And a crank angle detection unit that detects a crank angle that is a position of a rotation angle of the crankshaft.
The controller is
The crankshaft is rotated from a stopped state by driving the permanent magnet starter motor,
While the crank angle of the crankshaft is in the low load region, fuel is injected into the intake passage by controlling the fuel injection device;
The crank angle of the crankshaft is detected by the engine temperature detection unit between the low load region and between the fuel injection device injecting fuel into the intake passage and the closing of the intake valve. Controlling the rotational speed of the permanent magnet starter motor so as to suppress an increase in rotational speed of the crankshaft based on the temperature of the four-stroke engine main body,
The four-stroke engine body is started by igniting the air-fuel mixture in the combustion chamber using the igniter while the crank angle of the crankshaft is in the high load region.

  With the above configuration, by controlling the rotational speed of the permanent magnet starter motor according to the temperature of the engine unit, it is possible to suppress the rotational speed of the crankshaft. Therefore, the fuel injection time can be extended to secure the fuel evaporation time according to the engine temperature. Further, since the permanent magnet type starter motor has a large torque at the time of low rotation, it is possible to secure sufficient energy for starting the engine. Therefore, the above-described configuration can improve the startability of the engine.

  (2) According to another aspect, the engine unit of the present invention preferably includes the following configuration. The control device is configured to detect the rotational speed of the permanent magnet starter motor by the engine temperature detection unit, and the rotational speed of the crankshaft when the temperature of the four-stroke engine main body is a first temperature is the engine temperature The rotational speed of the permanent magnet starter motor such that the temperature of the four-stroke engine body detected by the detection unit is lower than the rotational speed of the crankshaft when the second temperature is higher than the first temperature. Control.

  Thus, when the temperature of the engine is low, the time for evaporation of the fuel is secured, so the startability of the engine can be improved.

  (3) According to another aspect, the engine unit of the present invention preferably includes the following configuration. The fuel injection device injects fuel toward the intake valve. By injecting the fuel in the vicinity of the intake port as described above, the efficiency of the fuel supply can be improved.

  (4) According to another aspect, the engine unit of the present invention preferably includes the following configuration. The control device determines the rotational speed of the crankshaft according to a fuel injection time determined based on the temperature of the four-stroke engine body detected by the engine temperature detection unit.

  Thereby, control of the fuel injection time according to the said engine temperature can be performed easily. Therefore, the start control of the engine can be performed more efficiently.

  (5) According to another aspect, the engine unit of the present invention preferably includes the following configuration. The engine temperature detection unit is a sensor that detects the temperature of the coolant in the four-stroke engine body or the temperature of the oil in the oil passage. Thus, the configuration of the engine unit can be simplified by sharing a sensor necessary as a function of the engine.

  (6) According to another aspect, the engine unit of the present invention preferably includes the following configuration. The control device causes the fuel injection device to inject the fuel within the fuel injection time until it exceeds a predetermined time that can supply the fuel necessary for starting the engine. As a result, the amount of fuel supplied to the engine can be maintained at a predetermined amount or more, and the startability of the engine can be improved.

  (7) According to another aspect, the engine unit of the present invention preferably includes the following configuration. The control device controls the rotational speed of the motor so as to lower the rotational speed of the crankshaft during the fuel injection time as the temperature of the four-stroke engine main body detected by the engine temperature detection unit decreases. . As a result, the time for fuel evaporation at low temperatures can be secured, and engine startability can be improved even at low temperatures.

  (8) According to another aspect, the engine unit of the present invention preferably includes the following configuration. The four-stroke engine body further includes a pressure reducing mechanism that temporarily opens the exhaust valve to exhaust the air-fuel mixture in the combustion chamber while the crank angle of the crankshaft is in the high load region. Thus, in a configuration having a pressure reducing mechanism, the first combustion at engine start may not be able to sufficiently increase the rotational speed of the crankshaft. On the other hand, by applying each of the above-described configurations, energy for starting the engine can be secured by the first combustion, so that the startability of the engine can be improved.

  The terminology used herein is for the purpose of defining particular embodiments only and is not intended to be limiting of the invention by said terminology. As used herein, "and / or" includes any and all combinations of one or more of the associated listed components.

  As used herein, the use of “including,” “including,” “comprising,” or “having,” and variations thereof, may be used to describe any of the described features, steps, elements, components, and / or , Identifying the existence of their equivalents, but may include one or more of steps, operations, elements, components, and / or groups thereof.

  As used herein, “attached”, “connected”, “coupled”, and / or their equivalents are used in a broad sense, “direct and indirect” attachment, Includes both connections and bonds. Furthermore, "connected" and "coupled" are not limited to physical or mechanical connections or couplings, but can include direct or indirect connections or couplings.

  Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

  Terms defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the related art and the meaning in the context of this disclosure, and unless explicitly defined otherwise herein. It is not to be interpreted in an ideal or overly formal sense.

  In the description of the present invention, it is understood that numerous techniques and steps are disclosed. Each of these has distinct benefits and can also be used with one or more, or possibly all, of the other disclosed techniques.

  Thus, for the sake of clarity, the description of the invention refrains from repeating every possible combination of the individual steps unnecessarily. However, the specification and claims should be read with the understanding that all such combinations are within the scope of the present invention.

  In the following description, numerous specific examples are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without these specific examples.

  Thus, the following disclosure should be considered as an illustration of the present invention, and is not intended to limit the present invention to the specific embodiments illustrated by the following drawings or description.

<Definition of cranking>
In the present specification, cranking refers to rotating the crankshaft by applying an external force from the outside of the engine regardless of combustion in a cylinder of the engine. In particular, cranking means that a motor for starting the engine is used to rotate a crankshaft at the time of starting the engine. Cranking also includes applying an external force to the crankshaft when combustion is occurring in a cylinder of the engine.

<Definition of high load area>
In the present specification, the high load range of the engine means a range in which the torque required for compression of the in-cylinder gas in the compression stroke is large in the operating range of the engine. The high load area of the engine includes the compression stroke.

<Definition of low load area>
In the present specification, the low load region of the engine means a region in which the in-cylinder gas is not compressed in the operating region of the engine.

<Definition of temperature of 4-stroke engine body>
In the present specification, the temperature of the four-stroke engine body means the temperature in the combustion chamber of the engine or the temperature detected by the engine temperature detection unit that detects the temperature related to the temperature in the combustion chamber. The temperature related to the temperature in the combustion chamber means the temperature, such as the coolant, the cylinder and crankcase body of the 4-stroke engine body, the fuel temperature, the injector temperature, the intake port temperature, which changes according to the temperature of the combustion chamber. . In the case of an air-cooled engine or the like, the temperature of the oil in the oil passage may be used.

  According to the engine unit according to one embodiment of the present invention, the startability of the engine can be improved.

FIG. 1 is a schematic view showing the configuration of the engine unit of the first embodiment. FIG. 2 is an explanatory view showing a relationship between a crank angle at engine start and a necessary torque necessary for cranking. FIG. 3 is a flow chart showing the operation of controlling the rotational speed of the permanent magnet starter motor by the ECU at the time of starting the engine unit of FIG. FIG. 4 is a view showing the relationship between the engine rotational speed and the crank angle at the start of the engine unit of FIG. FIG. 5 is a view for explaining an example of the movement of the crankshaft at the start of the engine unit shown in FIG. FIG. 6 is a graph schematically showing the relationship between the opening amount of the exhaust valve of the engine unit shown in FIG. 1 and the crank angle. FIG. 7 is a graph showing the engine rotational speeds when the engine temperature is high and low, respectively, when the engine unit of FIG. 1 is started. FIG. FIG. 8A is a graph showing an example of the relationship between the engine temperature and the rotational speed of the crankshaft at the time of engine start. FIG. 8B is a graph showing another example of the relationship between the engine temperature and the rotational speed of the crankshaft at the time of engine start. FIG. 9 is an explanatory view showing a schematic configuration of an engine unit, an example of a relationship between an engine temperature and a rotational speed of a crankshaft at engine start, and a relationship between a crank angle at engine start and a required torque. FIG. 10 is a schematic view showing the configuration of the engine unit of the second embodiment. FIG. 11 is a graph showing an example comparing the case where the fuel injection position is different in the relation between the engine temperature and the rotational speed of the crankshaft at the time of engine start.

First Embodiment
Hereinafter, embodiments will be described with reference to the drawings. In the drawings, the same portions are denoted by the same reference numerals, and the description of the same portions will not be repeated. In addition, the dimension of the structural member in each figure does not faithfully represent the dimension of an actual structural member, the dimensional ratio of each structural member, etc.

<Configuration of engine unit>
The configuration of engine unit 100 will be described. Engine unit 100 is provided in a motorcycle, which is an example of a vehicle. FIG. 1 is a schematic view showing the configuration of the engine unit 100. As shown in FIG. In the following, a case where the engine unit 100 has a single-cylinder four-stroke engine main body 10 (hereinafter simply referred to as the engine 10) will be described. In FIG. 1, each component of the engine unit 100 is simplified and shown. The engine unit 100 according to the present embodiment is an engine unit having a four-stroke engine 10 whose intake stroke, compression stroke, expansion stroke and exhaust stroke are included in one cycle.

  As shown in FIG. 1, the engine unit 100 includes an engine 10, an air cleaner 12, an intake pipe 14a, an intake pipe 14b, an exhaust pipe 16, a throttle device 20, a throttle position sensor (hereinafter referred to as TPS) 22, and a pressure sensor. 24, crank angle sensor 26 (crank angle detection unit), engine temperature sensor 28 (engine temperature detection unit), permanent magnet starter motor 30 and engine control unit (control unit, hereinafter referred to as ECU) 32, inverter 62 , A battery 64 and a start switch 66. First, components other than the engine 10 will be briefly described.

  The air cleaner 12 sucks air in the atmosphere (air outside the vehicle on which the engine 10 is mounted) and purifies the sucked air. One end of the intake pipe 14 a is connected to the air cleaner 12. The other end of the intake pipe 14 a is connected to a throttle body 20 c described later of the throttle device 20. One end of the intake pipe 14 b is connected to the throttle body 20 c of the throttle device 20. The other end of the intake pipe 14b is connected to a passage 34a formed in a cylinder head 34 described later. One end of the exhaust pipe 16 is connected to a passage 34 b formed in a cylinder head 34 described later. In the present embodiment, for example, an intake passage 33a is formed by the space in the intake pipe 14a, the space in the throttle body 20c, the space in the intake pipe 14b, and the passage 34a. Further, in the present embodiment, for example, the exhaust passage 33 b is formed by the passage 34 b and the space in the exhaust pipe 16.

  The intake passage 33a guides the air in the atmosphere purified by the air cleaner 12 into a combustion chamber 36 described later of the engine 10 through an intake port 35a described later. On the other hand, the exhaust passage 33b discharges the gas in the combustion chamber 36 to the atmosphere (outside of the vehicle) through an exhaust port 35b described later.

  The configuration of the intake passage 33a is not limited to the configuration shown in FIG. 1, and may be any configuration as long as air in the atmosphere can be introduced into the combustion chamber 36 described later. Further, the configuration of the exhaust passage 33b is not limited to the configuration shown in FIG. 1, and may be a configuration capable of discharging the gas in the combustion chamber 36 to the atmosphere. In the following description, "upstream" and "downstream" mean "upstream" and "downstream" based on the flow direction of air flowing from the air cleaner 12 to the exhaust passage 33b through the intake passage 33a and the engine 10. Do.

  The throttle device 20 includes a throttle valve 20a, a drive device 20b for driving the throttle valve 20a, and a throttle body 20c. The throttle valve 20a and the drive device 20b are provided on the throttle body 20c. For example, an electric motor can be used as the drive device 20b.

  The throttle valve 20a adjusts the opening area of the intake passage 33a by being driven by the drive device 20b. That is, in the present embodiment, the throttle valve 20a is an adjusting valve that adjusts the opening area of the intake passage 33a. The drive device 20 b is controlled by the ECU 32 as described later.

  The TPS 22 detects the position of the throttle valve 20 a as the throttle opening degree. The TPS 22 outputs a signal indicating the detected throttle opening degree to the ECU 32.

  The pressure sensor 24 detects the pressure (intake pressure) of a portion downstream of the throttle valve 20a in the intake passage 33a. That is, the pressure sensor 24 detects the pressure in a portion of the intake passage 33a between the throttle valve 20a and the combustion chamber 36 described later. In the following, the intake pressure means the pressure in a portion of the intake passage 33a between the throttle valve 20a and the combustion chamber 36. The pressure sensor 24 outputs a signal related to the detected pressure to the ECU 32. In the present embodiment, the pressure sensor 24 is a pressure detection unit.

  The crank angle sensor 26 detects a rotational position (hereinafter referred to as a crank angle) of the crankshaft 46 described later of the engine 10. The crank angle sensor 26 outputs a signal (crank pulse signal) indicating the detected crank angle to the ECU 32.

  Further, the ECU 32 ignites the air-fuel mixture in the combustion chamber 36 by an ignition plug 56 described later of the engine 10 based on the signal output from the crank angle sensor 26.

  The configuration and operation of the above-described ECU 32 are the same as those in the related art, and thus detailed description of the configuration and operation of the ECU 32 is omitted.

  The ECU 32 performs operation control at engine start. Specifically, the ECU 32 has a rotational speed calculation unit 70, a crank angle determination unit 71, a fuel injection time determination unit 72, a motor control unit 73, a fuel injection control unit 74, an ignition control unit 75, and a memory 76.

  The rotational speed calculator 70 calculates the rotational speed of the engine 10, that is, the rotational speed of the crankshaft 46 based on the crank pulse signal output from the crank angle sensor 26. The rotational speed of the crankshaft 46 calculated by the rotational speed calculation unit 70 is input to the motor control unit 73, and is used for feedback control of the permanent magnet starter motor 30.

  The crank angle determination unit 71 determines whether the crank angle obtained based on the crank pulse signal output from the crank angle sensor 26 is larger than a predetermined angle, and at the same time, the specified angle at which the crank angle starts fuel injection Determine if it is greater than. The determination result by the crank angle determination unit 71 is input to the motor control unit 73 and used for drive control of the permanent magnet starter motor 30. Further, the determination result by the crank angle determination unit 71 is input to the fuel injection control unit 74 and is used for drive control of the fuel injection device 54 described later of the engine 10. The predetermined angle is an angle smaller than the specified angle.

  The fuel injection time determination unit 72 obtains a fuel injection time according to the engine temperature from the injection time data stored in advance in the memory 76 based on the engine temperature information output from the engine temperature sensor 28. The fuel injection time determination unit 72 calculates the integrated time of fuel injection (integrated fuel injection time) when injecting fuel from the fuel injection device 54, and the calculated integrated fuel injection time is a predetermined value It is determined whether it is longer than (predetermined time).

  In addition, the engine temperature sensor 28 is a sensor which measures the temperature of the cooling fluid of the engine 10 as an example. The engine temperature sensor 28 may measure the temperature in the combustion chamber 36 directly, or may measure the temperature of the cylinder 40 of the engine 10, the crankcase 44, and the like. That is, the engine temperature sensor 28 may be provided at any position as long as the temperature associated with the combustion chamber 36 of the engine 10 can be measured.

  The motor control unit 73 is a permanent magnet starter motor based on the rotational speed of the crankshaft 46 output from the rotational speed calculation unit 70 and the determination result output from the crank angle determination unit 71 at engine start-up. Control 30 drives. Specifically, the motor control unit 73 controls the rotational speed of the permanent magnet starter motor 30 according to the determination result output from the crank angle determination unit 71, and also determines the rotational speed of the crankshaft 46. The feedback control of the permanent magnet starter motor 30 is performed using this.

  The fuel injection control unit 74 causes the fuel injection device 54 to inject fuel when the crank angle determination unit 71 determines that the crank angle is larger than a specified angle at which fuel injection is started. On the other hand, the fuel injection control unit 74 stops the fuel injection by the fuel injection device 54 when the fuel injection time determination unit 72 determines that the integrated fuel injection time is longer than the predetermined value.

  The ignition control unit 75 causes the spark plug 56 to ignite when the crank angle obtained based on the crank pulse signal output from the crank angle sensor 26 reaches the ignition timing of the spark plug 56.

  The permanent magnet starter motor 30 is a motor that starts the engine 10 by cranking the crankshaft 46. In the present embodiment, the permanent magnet starter motor 30 is a DC brushless motor. The permanent magnet starter motor 30 has a feature that the lower the rotational speed, the higher the torque.

  As the DC brushless motor, it is also possible to use a DC brushless motor of a type in which an electrical angle is detected by a Hall sensor, and a DC brushless motor of a type in which a mechanical angle is detected by a crank pulse.

  An output shaft of the permanent magnet starter motor 30 is connected to a crankshaft 46 of the engine 10 so as to rotate the crankshaft 46. In this embodiment, the output shaft of the permanent magnet starter motor 30 is connected to the crankshaft 46 without a power transmission mechanism (for example, a belt, a chain, a gear, a reduction gear, a speed increasing gear, etc.). . However, the permanent magnet type starter motor 30 may be connected to the crankshaft 46 of the engine 10 so that the crankshaft 46 can rotate in the positive direction. Therefore, the permanent magnet starter motor 30 may be connected to the crankshaft 46 via a power transmission mechanism. Preferably, the rotation axis of the permanent magnet starter motor 30 and the rotation axis of the crankshaft 46 substantially coincide with each other.

  The inverter 62 controls the rotational speed of the permanent magnet starter motor 30 by controlling the current supplied from the battery 64 to the permanent magnet starter motor 30. The inverter 62 is controlled by a motor control unit 73 of the ECU 32.

  The battery 64 supplies power to the permanent magnet starter motor 30 via the inverter 62.

  The start switch 66 outputs an on signal when starting the engine 10, according to the operation of the driver, or when an engine start condition is satisfied in an idle stop system described later. When an on signal is output from the start switch 66, the ECU 32 starts control of the rotational speed of the permanent magnet starter motor 30 in order to start the engine 10.

  Next, the configuration of the engine 10 will be described. In addition, since the structure of a well-known various engine can be employ | adopted as a structure of the said engine 10, detailed description of each component is abbreviate | omitted.

  The engine 10 includes a cylinder head 34, a cylinder 40, a piston 42, a crankcase 44, a crankshaft 46, a connecting rod 48, an intake valve 50, an exhaust valve 52, a fuel injection device 54 and an ignition plug 56 (ignition device).

  The piston 42 can reciprocate in the cylinder 40. The crankshaft 46 is capable of rotational movement within the crankcase 44. The piston 42 and the crankshaft 46 are connected by the connecting rod 48. The reciprocating motion of the piston 42 is transmitted to the crankshaft 46 via the connecting rod 48. Thereby, the crankshaft 46 rotates.

  In the engine 10, a combustion chamber 36 is formed by the cylinder head 34, the cylinder 40 and the piston 42. An intake port 35a and an exhaust port 35b are provided in the combustion chamber 36. In the cylinder head 34, a passage 34a connected to the intake port 35a and a passage 34b connected to the exhaust port 35b are formed. In the present embodiment, the intake pipe 14b and the combustion chamber 36 are connected by the passage 34a. Further, the combustion chamber 36 and the exhaust pipe 16 are connected by the passage 34b.

  The intake valve 50 opens and closes the intake port 35a. The exhaust valve 52 opens and closes the exhaust port 35b. The intake valve 50 is driven by a known valve mechanism not shown. Similarly, the exhaust valve 52 is driven by a valve mechanism (not shown).

  In one cycle, the intake valve 50 opens before the exhaust valve 52 closes and closes before the exhaust valve 52 opens. In other words, at least in the low load operation region, the suction stroke is started before the end of the exhaust stroke.

  Specifically, the intake valve 50 is opened at a crank angle of, for example, 344 degrees to 576 degrees. The crank angle in which the intake valve 50 is in the open state is not limited to the above, and may be in the open state at a minimum of 360 degrees to 540 degrees and at a maximum of 326 degrees to 610 degrees.

  Further, the exhaust valve 52 is open at least in the exhaust stroke. Specifically, the exhaust valve 52 is opened at a crank angle of, for example, 64 degrees to 378 degrees. The crank angle in which the exhaust valve 52 is open is not limited to the above, and may be open at a minimum of 180 degrees to 360 degrees, and at a maximum of 70 degrees to 390 degrees.

  The fuel injection device 54 injects fuel into the intake passage 33a. In the present embodiment, the fuel injection device 54 injects fuel toward the intake valve 50. The fuel supplied into the intake passage 33a is sent to the combustion chamber 36 as an air-fuel mixture together with air. The spark plug 56 ignites the mixture in the combustion chamber 36.

  The fuel injection device 54 and the spark plug 56 perform fuel injection and ignition at appropriate timing according to each stroke in one cycle of the engine 10 under the control of the ECU 32.

  Further, a pressure reducing mechanism 58 is provided in the vicinity of a cam shaft (not shown) for driving the exhaust valve 52. The pressure reducing mechanism 58 reduces the increase in resistance to the rotation of the crankshaft 46 caused by the compression of the air in the cylinder in the compression process of the engine. That is, the pressure reducing mechanism 58 is a mechanism that opens the exhaust valve 52 at a predetermined timing in order to reduce the pressure in the cylinder in the compression process at the start of the engine.

<Starting operation of engine unit>
First, the torque required for cranking when the engine is started will be described. FIG. 2 is an explanatory view showing a relationship between a crank angle at engine start and a necessary torque necessary for cranking.

  The engine 10 of the engine unit 100 has a high load area TH where the load for rotating the crankshaft 46 is large and a load for rotating the crankshaft 46 is smaller than the load of the high load area TH during four strokes. And a low load region TL. At the crank angle of the crankshaft 46, the low load area TL is equal to or larger than the high load area TH. More specifically, the low load area TL is wider than the high load area TH. In other words, the rotation angle area corresponding to the low load area TL is wider than the rotation angle area corresponding to the high load area TH.

  More specifically, the engine 10 repeats four strokes of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. As shown in FIG. 2, the compression stroke is included in the high load area TH but not included in the low load area TL. In the engine 10 of the present embodiment, the high load area TH is an area substantially overlapping with the compression stroke, and the low load area TL is an area substantially overlapping with the intake stroke, the expansion stroke, and the exhaust stroke. However, the boundaries between the high load region TH and the low load region TL do not have to coincide with the boundaries of the above-described respective strokes.

  In the compression stroke, since the air-fuel mixture in the combustion chamber 36 is compressed by the piston 42, a reaction force is generated by the compression. Therefore, in the compression stroke, the torque required for cranking is larger than in the other strokes. By operating the pressure reducing mechanism 58 in the compression stroke, the pressure in the combustion chamber 36 can be reduced.

  The pressure reducing mechanism 58 operates to open the exhaust valve 52 at a crank angle of approximately 630 degrees. The period during which the exhaust valve 52 is opened by the pressure reducing mechanism 58 is a short period of the compression stroke. Further, as shown in FIG. 6, the timing at which the exhaust valve 52 is opened by the pressure reducing mechanism 58 is immediately before the intake valve 50 is closed or after the intake valve 50 is closed. The timing at which the exhaust valve 52 is opened by the pressure reducing mechanism 58 can be adjusted within the compression stroke, as shown in FIG. Further, the valve lift amount of the exhaust valve 52 during the operation period of the pressure reducing mechanism 58 is smaller than the valve lift amount of the intake valve 50. The valve lift amount is the distance the valve moved axially away from the valve seat.

  Next, the starting operation of the engine unit 100 will be described. In the present embodiment, when the engine 10 is started, cranking by the starter motor 30 is performed. The start of the engine 10 includes the case where the engine 10 starts from a state where the engine temperature is lower than the temperature at the time of operation of the engine 10, and restart from the engine stop state in the idle stop system. In addition, since the idle stop system has the same structure as the conventional one, detailed description and illustration regarding the idle stop system are omitted.

  FIG. 3 is a flowchart showing an operation of controlling the rotational speed of the permanent magnet starter motor 30 by the ECU 32 at the start of the engine unit 100. FIG. 4 is a view showing the relationship between the engine rotational speed and the crank angle at the start of the engine unit 100. As shown in FIG. FIG. 5 is a view for explaining an example of the movement of the crankshaft 46 when the engine unit 100 is started.

  First, when the start switch 66 is turned on and the start request flag is set (step S1), the ECU 32 causes the motor control unit 73 to rotationally drive the permanent magnet starter motor 30.

  The engine 10 stops the combustion according to the combustion stop instruction of the ECU 32. The crankshaft 46 is rotated by inertia force after the combustion in the engine 10 is stopped. When the inertial force becomes smaller than the compression reaction force in the compression stroke of the engine 10, the crankshaft 46 is reversely rotated and stopped by the compression reaction force. Therefore, as shown in FIG. 5, the stop position of the crankshaft 46 is often stopped at a crank angle P0 of an intake stroke which is a stroke before a compression stroke.

  The ECU 32 obtains information on the crank angle and the rotational speed of the engine 10 based on the signal output from the crank angle sensor 26. When the crank angle of the crankshaft 46 is not at the specified position, the motor control unit 73 of the ECU 32 reversely rotates the permanent magnet starter motor 30 as shown by a broken line in FIGS. 4 and 5. The reverse rotation of the permanent magnet starter motor 30 is continued until the crank angle reaches the defined position P1 in the expansion stroke.

  Subsequently, the crank angle determination unit 71 of the ECU 32 determines whether the crank angle of the crankshaft 46 is larger than a predetermined angle (step S2). The predetermined angle is an angle smaller than a crank angle (prescribed angle) at which fuel is injected.

  When the crank angle of the crankshaft 46 is larger than the predetermined angle (YES in step S2), the motor control unit 73 of the ECU 32 causes the rotational speed of the crankshaft 46 to be the target rotational speed A, The drive control of the permanent magnet type starter motor 30 is performed (step S3). The control of the rotational speed of the permanent magnet starter motor 30 may be torque control using a duty ratio, or may be speed control in which the rotational speed of the permanent magnet starter motor 30 is detected and feedback control is performed.

  The target rotational speed A has, as an upper limit, a speed capable of securing a fuel injection time derived from the engine temperature measured by the engine temperature sensor 28 as described later, and a speed capable of overcoming the maximum load in the high load area TH. Is the lower limit.

  When the rotational speed of the crankshaft 46 is low, the vaporized fuel can not be compressed in the high load region TH, and the engine 10 is stopped.

  On the other hand, when the rotational speed of the crankshaft 46 is large, the time for the injected fuel to evaporate may not be sufficiently secured. In this case, the concentration of fuel in the combustion chamber 36 of the engine 10 is insufficient, which may lead to an increase in the rotational speed of the engine 10 and a misfire.

  That is, when the rotational speed of the crankshaft 46 at the time of cranking becomes extremely large, evaporation of fuel is not sufficiently performed in the passage 34a of the intake passage 33a after the fuel injection time FI (see FIG. 4) has elapsed. As a result, the air-fuel ratio in the combustion chamber 36 may not be an appropriate value.

  The target rotational speed A of the crankshaft 46 is determined within the range of the upper limit and the lower limit in consideration of the phenomenon as described above. The target rotational speed A is obtained based on the temperature of the engine 10 as described later.

  If the crank angle of the crankshaft 46 is equal to or less than the predetermined angle (NO in step S2), the crank angle determination unit 71 proceeds to step S2 until the crank angle of the crankshaft 46 becomes larger than the predetermined angle. Repeat the determination.

  After the permanent magnet starter motor 30 is driven and controlled at the target rotational speed A, the crank angle determination unit 71 determines whether the crank angle of the crankshaft 46 is larger than a specified angle for starting fuel injection. (Step S4). If the crank angle of the crankshaft 46 is larger than the specified angle for starting fuel injection (YES in step S4), the fuel injection control unit 74 of the ECU 32 causes the fuel injection device 54 to inject fuel (step S5). . On the other hand, when the crank angle of the crankshaft 46 is less than or equal to the specified angle for starting fuel injection (in the case of NO in step S4), the crank angle of the crankshaft 46 becomes larger than the specified angle for starting fuel injection; The determination in step S4 is repeated.

  In the present embodiment, the prescribed angle of fuel injection start by the fuel injection device 54 is, for example, 300 °. However, the prescribed angle of the fuel injection start may be other than 300 °. As described above, the fuel injection time is determined by the fuel injection time determination unit 72 based on the injection time data previously determined based on the engine temperature. The injection time data is stored in the memory 76 of the ECU 32. In addition, it is necessary to finish fuel injection from the start of fuel injection to the closing of the intake valve 50 (within the period of FI shown in FIG. 4) at the longest.

  After the fuel injection by the fuel injection device 54 is started, the fuel injection time determination unit 72 of the ECU 32 determines whether the integrated fuel injection time which is the integration time of the fuel injection is larger than the predetermined value (predetermined time) of the fuel injection time It is determined whether or not (step S6). If it is determined that the integrated fuel injection time is longer than the predetermined value (YES in step S6), the fuel injection by the fuel injection device 54 is stopped (step S7). Thereafter, the rotational speed control in which the target rotational speed is set to A in step S3 is canceled (step S8), and the flow of the rotational speed control at the time of engine start is ended (end). The predetermined value is determined according to the engine temperature using the injection time data.

  On the other hand, when it is determined that the integrated fuel injection time is equal to or less than the predetermined value (in the case of NO in step S6), the fuel by the fuel injection device 54 is until the integrated fuel injection time becomes larger than the predetermined value. Continue the injection.

  After the rotational speed control of the permanent magnet starter motor 30 by the ECU 32 described above, when the intake valve 50 is closed, the compression pressure in the combustion chamber 36 becomes the rotational load of the crankshaft 46 in the subsequent compression stroke. . Thus, as shown in FIG. 4, the rotational speed of the crankshaft 46 is reduced. After the crankshaft 46 passes a position corresponding to the compression top dead center in the compression stroke, the ignition control unit 75 of the ECU 32 causes the ignition plug 56 to ignite the mixture in the combustion chamber 36, thereby performing the first combustion. Is done. In the present embodiment, although the crank angle at the time of ignition of the spark plug 56 is 715 degrees, it is not limited to this.

  As a result of the first combustion described above, torque is applied to the crankshaft 46, and each stroke of four cycles is continuously performed by the engine 10, whereby starting of the engine 10 by cranking is completed.

<Determination procedure of target rotational speed>
Next, the procedure for determining the target rotational speed A of the crankshaft 46 at the start of the engine 10 will be described.

  The fuel injection time determination unit 72 of the ECU 32 refers to the injection time data stored in the memory 76 of the ECU 32 in advance, based on the temperature of the engine 10 measured by the engine temperature sensor 28. Determine the fuel injection time for the first combustion at the start of the engine.

  The injection time data is, for example, a table in which an engine temperature and a fuel injection time are associated with each other. The injection time data is set such that the fuel injection time becomes longer as the engine temperature is lower. The injection time may be calculated to be longer according to a predetermined relational expression as the temperature decreases, or the injection time is constant within a certain predetermined range, and becomes shorter when the engine temperature becomes higher than the range. It may be set to be In addition, an example of the said injection time is shown by the continuous line arrow in FIG. As shown in FIG. 2, the injection time when the engine temperature is −5 ° C. is longer than the injection time when the engine temperature is 80 ° C. In FIG. 2, only the first stroke of the injection time is described, and the description of the subsequent strokes is omitted.

  Further, the injection time data changes depending on the position at which the fuel injection device 54 injects fuel, the injection direction, the size of droplets of the fuel to be injected, and the like. As described above, even when the temperature of the engine 10 is low, the injected fuel is sufficiently evaporated to obtain an appropriate air-fuel ratio at the time of ignition. Therefore, the injection time data is set so that the fuel injection time becomes longer when the engine temperature is low. Generally, the smaller the droplet size of the fuel to be injected and the larger the spread angle of the spray, the shorter the injection time.

  The injection of fuel by the fuel injection device 54 is started at a predetermined crank angle (for example, 300 degrees) and is completed by the time the intake valve 50 is closed in the intake stroke of the engine 10. For this reason, it is necessary to determine the rotational speed of the crankshaft 46 so that the injection of fuel is completed before the intake valve 50 opens. In the present embodiment, the fuel injection start timing is fixed at a crank angle of 300 degrees regardless of the engine temperature.

  Therefore, in order to secure the fuel injection time at low temperature, it is necessary to set the target rotational speed A of the crankshaft 46 according to the time from the start of fuel injection to the closing of the intake valve 50. Therefore, as shown in FIG. 7, the target rotational speed A is set to be lower as the injection time becomes longer. As described above, since the fuel injection time needs to be longer as the engine temperature is lower, as shown in FIG. 7, the target rotational speed A 'when the engine temperature is low is the target rotation when the engine temperature is high. It is lower than speed A.

  FIG. 8A shows an example of the relationship between the engine temperature and the rotational speed of the crankshaft 46 at the time of engine start. As described above, the target rotational speed A of the crankshaft 46 becomes lower as the temperature of the engine 10 becomes lower. As one example, as shown in FIG. 8A, at temperatures of the engine 10 at arbitrary two points in the graph (respectively referred to as first and second temperatures), the crankshaft 46 at a relatively low first temperature. The ECU 32 controls the rotational speed of the permanent magnet starter motor 30 so that the rotational speed is lower than the rotational speed at a second temperature higher than the first temperature.

  The rotational speed of the crankshaft 46 does not change continuously according to the temperature of the engine 10 as described above, but as shown in FIG. 8B, the temperature of the engine 10 is constant up to a predetermined temperature. When the temperature of the engine 10 becomes lower than the predetermined temperature, control may be performed to lower the rotational speed.

  As described above, the fuel injection may be completed (fuel injection time FI) from the start of the fuel injection to the closing of the intake valve 50. Therefore, the fuel injection time of the injection time data may be shorter than the fuel injection time FI.

  By the way, if the target rotational speed of the crankshaft 46 is increased according to the fuel injection time, the power consumption of the permanent magnet starter motor 30 is increased, and the power consumption of the battery 64 is increased. On the other hand, the target rotational speed A of the crankshaft 46 may be reduced to a rotational speed that can ensure the required fuel injection time according to the engine temperature. Thereby, the power consumption of the permanent magnet type starter motor 30 can be suppressed, and the increase of the power consumption of the battery 64 can be suppressed.

  According to the engine unit 100 according to the present embodiment, as the starter motor, a permanent magnet starter motor 30 is used which can obtain higher output torque as the rotational speed is lower. Further, in the engine 10 in which the high load area TH and the low load area TL exist between the four strokes, as shown in FIG. 5, the low load area to the first combustion after the crankshaft 46 rotates from the stop state. The target rotational speed A of the crankshaft 46 is set according to the engine temperature by TL. As a result, it is possible to secure time for the fuel supplied into the intake passage 33a to be vaporized. Therefore, the energy from the first combustion can be sufficiently increased, and the startability of the engine 10 can be improved.

  Further, in the present embodiment, the pressure in the combustion chamber 36 can be reduced by operating the pressure reducing mechanism 58 in the compression stroke at engine start. However, by operating the pressure reducing mechanism 58 in the compression process, sufficient energy may not be obtained in the first combustion at engine start, and the rotational speed of the crankshaft 46 may not be increased. On the other hand, in the engine unit 100 of the present embodiment, the target rotational speed A of the crankshaft 46 is adjusted according to the engine temperature in the low load region TL until the first combustion after the crankshaft 46 rotates from the stopped state. By setting the time, it is possible to secure the time for the fuel supplied into the intake passage 33a to be vaporized. Therefore, the energy from the first combustion can be sufficiently increased, and the startability of the engine 10 can be improved.

Second Embodiment
FIG. 10 is a schematic view showing a configuration of an engine unit 101 according to a second embodiment of the present invention. In the engine unit 101 according to the present embodiment, the ECU 80 sets the rotational speed of the crankshaft 46 according to the temperature of the engine 10 using rotational speed data as map data of the engine temperature and the target rotational speed A. Is different from the engine unit 100 according to the first embodiment.

  Specifically, the ECU 80 includes a rotational speed calculation unit 70, a crank angle determination unit 71, a motor control unit 73, a fuel injection control unit 74, an ignition control unit 75, a memory 76, and a rotational speed determination unit 81.

  In this embodiment, in addition to the injection time data similar to that of the first embodiment, the memory 76 is a map in which the temperature of the engine 10 and the target rotational speed A of the crankshaft 46 at the time of engine start are associated in advance. The rotational speed data as data is stored.

  The rotational speed determination unit 81 uses the rotational speed data stored in the memory 76 to determine the target rotational speed A of the crankshaft 46 at engine start-up according to the engine temperature measured by the engine temperature sensor 28. Do. The motor control unit 73 controls the inverter 62 using the target rotation speed A determined by the rotation speed determination unit 81, such that the crankshaft 46 has the target rotation speed A, and the permanent magnet starter motor Drive 30.

  The fuel injection control unit 74 uses the rotational speed data stored in the memory 76 to determine the fuel injection time in accordance with the engine temperature measured by the engine temperature sensor 28. The method of determining the fuel injection time is the same as that of the first embodiment. The fuel injection time may be determined according to the rotational speed of the crankshaft 46.

  The configuration of the ECU 80 other than the above is the same as that of the ECU 32 of the first embodiment, and thus the detailed description of the ECU 80 is omitted.

  Also according to the configuration of the present embodiment, it is possible to secure time for the fuel supplied into the intake passage 33a to be vaporized. Therefore, the energy from the first combustion can be sufficiently increased, and the startability of the engine 10 can be improved.

(Other embodiments)
As mentioned above, although embodiment of this invention was described, embodiment mentioned above is only an illustration for implementing this invention. Therefore, without being limited to the embodiment described above, the embodiment described above can be appropriately modified and implemented without departing from the scope of the invention.

  In each of the above embodiments, the engine unit using a single cylinder 4-stroke engine has been described, but the engine may be a parallel 2-cylinder or V-type 2-cylinder 4-stroke engine.

  In each of the above embodiments, the case where the crankshaft 46 is reversely rotated at the time of engine start has been described. However, the present invention is not limited to this. The crankshaft 46 may be normally rotated at the time of engine start without reverse rotation.

  The permanent magnet starter motor 30 used in each of the above embodiments may be a motor having a brush or a brushless motor. Also, the starter motor may be a starter motor generator that also has a generator function.

  In the above embodiments, the fuel injection device 54 injects fuel toward the intake valve 50, but may inject fuel to another position in the intake passage 33a. For example, the position where the fuel injection device 54 injects fuel may be injected upstream of the intake valve 50 and toward the inner surface of the wall constituting the intake passage 33a.

  In this case, the injection time data can be set so that the injection time is longer than when the fuel is injected toward the intake valve 50. That is, as shown in FIG. 11, the target rotational speed A of the crankshaft 46 in the case of injecting toward the inner surface of the wall constituting the intake passage 33a is the case of injecting fuel toward the intake valve 50. Low compared to.

  In the above embodiments, the configuration in which the engine units 100 and 101 are applied to a motorcycle has been described. However, the engine unit 100, 101 may be applied to other vehicles such as a three-wheeled vehicle or a four-wheeled vehicle.

  In the above embodiment, the temperature of the engine coolant was measured as the temperature of the engine 10. For example, in the case of an air-cooled engine, the temperature of the oil in the oil passage through which the lubricating oil flows as the temperature of the engine. May be measured.

  Although the engine 10 uses the TPS 22 in the above embodiment, an accelerator position sensor may be used instead of the TPS 22.

  In the first embodiment, the engine unit 100 includes the pressure reducing mechanism 58. The engine unit 101 of the second embodiment may also be provided with a pressure reducing mechanism. The engine unit 100 may not have a pressure reducing mechanism.

10 four-stroke engine body 12 air cleaners 14a and 14b intake pipe 16 exhaust pipe 20 throttle device 22 TPS
24 Pressure sensor 26 Crank angle sensor (crank angle detector)
28 Engine temperature sensor (engine temperature detector)
30 Permanent magnet type starter motor 32, 80 ECU (control device)
33a intake passage 33b exhaust passage 35a intake port 35b exhaust port 34 cylinder head 36 combustion chamber 40 cylinder 42 piston 44 crankcase 46 crank shaft 46 connecting rod 50 intake valve 52 exhaust valve 54 fuel injection device 56 spark plug (ignition device)
58 decompression mechanism 62 inverter 64 battery 66 start switch 70 rotation speed calculation unit 71 crank angle determination unit 72 fuel injection time half bottom 73 motor control unit 74 fuel injection time control unit 75 ignition control unit 76 memory 81 rotation speed determination unit 100, 101 Engine unit

Claims (8)

A combustion chamber provided with an intake port and an exhaust port, an intake valve for opening and closing the intake port, an exhaust valve for opening and closing the exhaust port, air connected to the intake port and air in the atmosphere via the intake port , An exhaust passage connected to the exhaust port, a fuel injection device for injecting fuel into the intake passage, and ignition for igniting a mixture including fuel and air in the combustion chamber Apparatus, a piston reciprocating in the combustion chamber, and a crankshaft connected to the piston so as to rotate according to the reciprocating movement of the piston, a load rotating the crankshaft during four strokes 4 stroke engine having a high load area where the load is large and a low load area where the load that rotates the crankshaft is smaller than the load of the high load area. And down the body,
A permanent magnet starter motor having a permanent magnet and rotating the crankshaft;
A controller for controlling the permanent magnet starter motor, the fuel injection device, and the ignition device;
An engine temperature detection unit that detects the temperature of the four-stroke engine body;
And a crank angle detection unit that detects a crank angle that is a position of a rotation angle of the crankshaft.
The controller is
The crankshaft is rotated from a stopped state by driving the permanent magnet starter motor,
While the crank angle of the crankshaft is in the low load region, fuel is injected into the intake passage by controlling the fuel injection device;
The crank angle of the crankshaft is detected by the engine temperature detection unit between the low load region and between the fuel injection device injecting fuel into the intake passage and the closing of the intake valve. Controlling the rotational speed of the permanent magnet starter motor so as to suppress an increase in rotational speed of the crankshaft based on the temperature of the four-stroke engine main body,
An engine unit for starting the four-stroke engine body by igniting the air-fuel mixture in the combustion chamber using the igniter while the crank angle of the crankshaft is in the high load range. In the engine unit according to claim 1,
The control device is configured to detect the rotational speed of the crankshaft when the temperature of the four-stroke engine main body detected by the engine temperature detection unit is a first temperature, by the engine temperature detection unit An engine unit controlling the rotational speed of the permanent magnet starter motor such that the rotational speed of the crankshaft is lower than the rotational speed of the crankshaft when the temperature of the main body is a second temperature higher than the first temperature. In the engine unit according to claim 1 or 2,
The engine unit, wherein the fuel injection device injects fuel toward the intake valve. The engine unit according to any one of claims 1 to 3.
The engine unit determines the rotational speed of the crankshaft according to a fuel injection time determined based on the temperature of the four-stroke engine body detected by the engine temperature detection unit. The engine unit according to any one of claims 1 to 4.
The engine unit, wherein the engine temperature detection unit is a sensor that detects a temperature of a coolant of the four-stroke engine body or a temperature of oil in an oil passage. The engine unit according to any one of claims 1 to 5.
The engine unit, wherein the control device causes the fuel injection device to inject fuel until the fuel injection time exceeds a predetermined time that can supply the fuel necessary for starting the engine. The engine unit according to any one of claims 1 to 6.
The control device controls the rotational speed of the motor so as to lower the rotational speed of the crankshaft during the fuel injection time as the temperature of the four-stroke engine main body detected by the engine temperature detection unit decreases. , Engine unit. The engine unit according to any one of claims 1 to 7.
The four-stroke engine body further includes a pressure reducing mechanism that temporarily opens the exhaust valve to discharge the air-fuel mixture in the combustion chamber while the crank angle of the crankshaft is in the high load region. unit.

Images